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Old Nov 06, 2002, 10:21 AM
Guybo is offline
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Turbo Fan


Just for interest I have posted a thread on the 'Aircraft Jets' forum of our latest development in gas turbine model aero engine. Seeing that you guy's seem interested in EDF, and fan design. My father a I have been working on our gas turbine equivilent for several years now, and have finally come up with a high bypass turbo fan, from our development of or turbo shaft gas turbine engines. A few stats for you interest.

Fan Diameter 180mm
Flow rate accros fan 100 m/s
Thrust 'static' 13 Kg (27 lbs)
Bypass Ratio 8:1
Core Mass Flow 0.18 Kg/s
Fan Mass Flow 1.6 Kg/s

The engine is still in development, were a focus of rotor dynamics is at our attention, dealing with the concrentric shaft which drives the fan from the free turbine wheel. The concentric shaft is a new development in small gas turbines were small diameters are required. In a result the fan drive shaft runs super critical, were its critical speed is around 18000rpm, getting through critical is the problem, but once through smooth running is achievable.
The gas generator section of the engine 'compressor combuster, and turbine' has a shaft speed of 160,000rpm, were the core engine is based on the excellent 'Wren MW54'. The Fan design speed max is 16000rpm, were 14000rpm is our constant speed limit. the fan is driven from the free turbine, were it drives a planatary gearbox in the hub of the fan, with a gear ratio od 3.76:1.

The engine has run 5 times now, were the last run with the latest shaft configuration was good, were just over half power was applied. We are slowly gaining confidence in running the engine, but it is nervouse buisness as things can go wrong, and a propper safty enclosure may be required.
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Old Nov 06, 2002, 11:55 AM
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WOW!! I have always thought that a turbo fan would be neat!
That is really something. Only problem, turbines are so spendy
Isaac.S
Old Nov 06, 2002, 12:44 PM
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Yes turbines are expensive, even when you make them your self!. But it is the hobby, so exceptions can be made.

One of these days I may have to make a plane for it, as you may of guessed it will be fairly large. I was thinking along the lines of a 777, or an A330. I was wondering what the best way to approach the scaling down of the plane, or what to scale from?. If anyone has any ideas if would great!!. An A-10 is another option, about 12' wing span!!!
Old Nov 06, 2002, 05:55 PM
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turbofan


for those that are interested here are some pics of my mates turbofan, it is very kool
Old Nov 06, 2002, 05:57 PM
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wood basher
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no.2


no.2
Old Nov 06, 2002, 05:59 PM
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no.3


no.3
Old Nov 06, 2002, 06:16 PM
Tim H. is offline
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Quote:
Originally posted by Guybo
Yes turbines are expensive, even when you make them your self!. But it is the hobby, so exceptions can be made.

One of these days I may have to make a plane for it, as you may of guessed it will be fairly large. I was thinking along the lines of a 777, or an A330. I was wondering what the best way to approach the scaling down of the plane, or what to scale from?. If anyone has any ideas if would great!!. An A-10 is another option, about 12' wing span!!!
OHHHHHH A big A-10 would be incredible!!!! The way I would do it is take a good scale 3-view (I have some good ones), import the image into a CAD program, size the image to get the inlet dia. to 180mm, then take the scale from there. I would LOVE to build a big A-10 like that but there is NO way I could ever afford 2 of those engines!

Tim H.
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Old Nov 06, 2002, 06:36 PM
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A-10


I see what you meen about taking the 3 - view drawing and working from there. I think this would be a good method, but what worries me is getting the fundimentlas right, i.e getting the wing instance to the fuz correct, and so for the tail plane. Another worrie may be the fact that the engines weigh about 2 kg each, so with them hanging out the back, and no gatling gun to counter may make things alittle interesting!!. Oh well engine number two is alittle way down the line to be finished, and engine number one is still being tested and developed, so I have alittle time to ponder those problems.

Guy
Old Nov 06, 2002, 06:37 PM
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A 1/6 scale A-10 would be the correct scale for the engines. That is taking the 180mm fan and fitting it to scale drawings.
Length = 114.07 inches
WS = 123.36 inches

Tim H.
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Old Nov 06, 2002, 06:39 PM
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That is awesome! Congrats on the great work and keep us informed!
Old Nov 06, 2002, 06:47 PM
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Thanks for the impressions.

an A -10 with a 10 foot wing span sounds superb!! , thanks for doing the conversions for me. Do you know were to find good 3 - view drawings of an A - 10 to work from.
I am begining to like the idea more as the A - 10 looks like a nice stable flyer!, the funny thing is that two jetcat 120's will do the same job, so I should think that there will be a few around or being biult as I type!.
Old Nov 06, 2002, 06:48 PM
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Here is a link to a German website. This A-10 may be right about 1/6 scale.

http://www.gueba-jets.de/deutsch/mod...0_warthog.html

Tim H.
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Old Nov 06, 2002, 07:35 PM
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Quote:
Originally posted by Guybo
Thanks for the impressions.

an A -10 with a 10 foot wing span sounds superb!! , thanks for doing the conversions for me. Do you know were to find good 3 - view drawings of an A - 10 to work from.
I am begining to like the idea more as the A - 10 looks like a nice stable flyer!, the funny thing is that two jetcat 120's will do the same job, so I should think that there will be a few around or being biult as I type!.
Send me a PM with your email and I'll send you the drawings I have. Sample below.

Tim H.
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Old Nov 06, 2002, 10:06 PM
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WOWWWW! I am absolutely amazed by the photos!
How does thrust to weight factor compare to regular turbines? And fuel?
Isaac.S
Old Nov 07, 2002, 05:35 AM
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Thrust to Weight


Thrust to weight of this engine will probably be alittle down if comparing to a pure jet engine like the jetcat p180, which can produce around 26 lb of thrust, but the P180 is a larger engine, and if the thrust was to be coupled to a free turbine, then a prop for instance the thrust would be 50 lb+. The core engine used on the turbo fan based on the MW54 from Wren, is half the size of the P180, and produces on its own about 12 lb of thrust, but we have done turbo prop versions, and turbo fan versions, were the the thrust achieved is 35 lb, and 27 lb respectively, which is what you would expect from the varying characterists of these engines.
Fuel comsuption in the other hand is in the favour of the turbo prop, and turbo fan engines, which are generally more efficient then pure jets. Pure jet engines have high verlocity exhaust gases, which enable high speed over the speed of sound, and at high altertudes, were turbo fans have less flow velocity, but higher mass flow, which enables speeds nearing the speed of sound, but can not reach the same altertudes before the efficiency drops off. Turbo props are the most efficient but efficencys drop off at lower altertudes and speeds, so the turbo fans generally bridges the gap between pure jet, and turbo prope. ( those comparisons are bases on full size engines, I think we are a way off from reaching the speed of sound with our small engines).

An example would be given a jet cat p180, and two litres of fuel, the duration would be about 6 mins, whilst given out turbo fan with the same amount of fuel, and static thrust, the duration would be about 10 - 15 mins
Sorry about that I went off on one there!!!!!

guy


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